This application is based upon U.S. Provisional Application Ser. No. 62/506,894 filed May 16, 2017, the complete disclosure of which is hereby expressly incorporated by this reference.
Engineers and digital artists often use three-dimensional (3D) scanners to create digital models of real-world objects. An object placed in front of the device can be scanned to make a 3D point cloud representing the surface geometry of the scanned object. The point cloud may be converted into a mesh importable into computers for reverse engineering, integration of hand-tuned components, or computer graphics.
Various methods of illumination, capture, and 3D mesh generation have been proposed. The most common illumination methods are structured light and laser line scanning. Most systems employ one or more cameras or image sensors to capture reflected light from the illumination system. Images captured by theses cameras are then processed to determine the surface geometry of the object being scanned. Structured light scanners have a number of advantages over laser line or laser speckle patterns, primarily a greatly increased capture rate. The increased capture rate is due to the ability to capture a full surface of an object without rotating the object or sweeping the laser. Certain techniques in structured light scanning enable the projection of a continuous illumination function (as opposed to the discrete swept line of a laser scanner) that covers the entire region to be captured; the camera or cameras capture the same region illuminated by the pattern. Traditionally, structured light scanners consist of one projector and at least one image sensor (camera). The projector and camera are typically fixed a known distance apart and disposed in such a fashion that the field of view of the camera coincides with the image generated by the projector. The overlap region of the camera and projector fields of view may be considered the capture volume of the 3D scanner system. An object placed within the capture volume of the scanner is illuminated with one or more patterns generated by the projector. Each of these patterns is often phase-shifted (i.e. a periodic pattern is projected repeatedly with a discrete spatial shift). Sequential images may have patterns of different width and periodicity. From the perspective of the camera, the straight lines of the projected image appear to be curved or wavy. Image processing of the camera's image in conjunction with the known separation of the camera and projector may be used to convert the distortion of the projected lines into a depth map of the surface of the object within the field of view of the system.
Among structured light scanners, pattern generation methods wherein a repeating pattern is projected across the full field of view of the scanner are the most common. An illumination source projects some periodic function such as a square binary, sinusoidal, or triangular wave. Some methods alter the position of an imaging substrate (e.g. a movable grating system) (See U.S. Pat. Nos. 5,581,352 and 7,400,413) or interferometers (See U.S. Pat. No. 8,248,617) to generate the patterns. The movement of the imaging substrate in these prior art methods requires very precise movement and the patterns generated will often have higher order harmonics which introduces spatial error. These disadvantages limit the applicability of movable grating systems for mass appeal.
The methods disclosed herein seek to solve the problems posed by existing movable imaging substrate techniques and devices. The present invention reduces cost, increases manufacturability and increases projection speed and thereby 3D capture speed over current systems.